This invention relates generally to heat exchangers, and more particularly to counter flow microchannel heat exchangers.
There are many industrial devices and processes wherein a component has to be maintained at a precise and uniform temperature. Examples of such devices and processes include optical devices and components, such as precision telescopes, solid-state lasers, and semiconductor laser diodes; wafer processing equipment in the semiconductor industry; and bio-processing containers in the pharmaceutical industry.
A suitable heat exchanger for these applications can be either of the microchannel type or the impingement type. Microchannel heat exchangers typically use unidirectional liquid coolant flow in a single layer of channels. While a microchannel heat exchanger is conducive to maintaining a very uniform temperature in a component in a direction perpendicular to the coolant flow, the lateral temperature parallel to the direction of coolant flow exhibits an increase as the liquid coolant receives heat. The temperature rise can be limited by increasing the coolant flow rate, but this results in a high pressure drop and poor coolant utilization. A 2-layer, 2-pass microchannel heat exchanger is described in U.S. Pat. No. 5,005,640, the contents of which are hereby incorporated by reference in their entirety. The 2-pass heat exchanger improves lateral temperature uniformity and coolant utilization. However, to achieve the second pass, the direction of coolant flow is reversed, which leads to a very high pressure drop.
Impingement type heat exchangers can provide uniform cooling, but exhibit very high pressure drop and poor coolant utilization.
For the foregoing reasons, there is a need for a microchannel heat exchanger which can provide substantially uniform cooling over a large area. The new microchannel heat exchanger should also handle high heat flux with a low pressure drop.